Ja En つくば宇宙フォーラム
第152回
Revisiting the small-scale crises of ΛCDM: new perspectives and insights
MA Hai-Xia 氏
名古屋大学
要旨
The ΛCDM paradigm has been remarkably successful in explaining the large-scale structure of the universe, from galaxy clustering to the cosmic microwave background. However, at smaller scales—both galactic and circum-galactic—observations reveal persistent discrepancies that challenge the standard model. These small-scale crises include the core-cusp problem, the missing satellites problem, the too-big-to-fail problem, and the empirical correlations between baryonic and dark matter dynamics, such as the radial acceleration relation (RAR). These unresolved tensions raise fundamental questions about the nature of dark matter and whether modifications to our current gravitational framework are needed. In this talk, I will present an analysis of the Milky Way’s dark matter distribution using Jeans equation constraints and kinematic data from Gaia DR3 and LAMOST DR8, incorporating approximately 878,000 red clump stars within |z| ≤ 5 kpc. By leveraging full three-dimensional velocity and velocity-dispersion data, we test the viability of different dark matter halo profiles and modified gravity models. Our results favor a slightly oblate dark matter halo with a core-like inner density profile, deviating from the cuspy Navarro-Frenk-White (NFW) profile predicted by ΛCDM simulations. These results provide new constraints on the nature of dark matter and highlight open questions regarding the underlying physical mechanisms driving the observed baryon-dark matter coupling. I will discuss the implications of these findings in the broader context of galaxy formation and the possible avenues for resolving the small-scale tensions within ΛCDM.